Physiological activities of certain organs (such as the heart and cerebrum) may be reflected by bioelectricity waves. The process of electrocardiography (ECG) or electroencephalography (EEG), in which lead wires are connected to the patient's chest or cerebrum, may assist a doctor in judging tissue lesions. A poor connection or even disconnection of a lead wire (i.e., when the lead wire has a disconnected state) will cause a detection failure. In existing lead wire detection techniques, each lead wire is connected to a constant current resource or a bias circuit, respectively, in which the bias circuit may include a voltage source and a megohm resistor. For example, in ECG detection, when a lead wire is connected to a human body, the human body impedance is much less than the output impedance of the corresponding bias circuit, and the voltage drop to the human impedance is small, so the voltage at the ECG front end is close to 0V, and the ECG measurement would not be affected. When the lead wire is disconnected, the impedance is infinity and the lead wire is driven to a certain voltage by the bias circuit. So the voltage at the ECG input channel would significantly vary when the lead wire is in a connected state or disconnected state. A system usually comprises an Analog-to-Digital Converter (ADC), and usually the ADC is used for cyclically sampling the voltage of the ECG input channel. A voltage threshold, which is between the voltages at the ECG input channel when the lead wire is in a connected state and disconnected state, is selected, and the connection status of the lead wire is determined by comparing sampled voltages with the voltage threshold. This approach requires a higher sampling rate of the ADC and increases the burden on the ADC, presenting system design difficulties and higher costs.